Prevalence and Prognostic Value of Individual T4-Defining Radiologic Features in Human Papillomavirus-Positive Oropharyngeal Carcinoma.

PURPOSE: To report the prevalence, validity, and relative prognostic value of specific UICC (Union for International Cancer Control)/AJCC (American Joint Committee on Cancer) T4-defining radiologic features in human papillomavirus-positive oropharyngeal squamous cell carcinoma (HPV+ OPSCC).

METHODS AND MATERIALS: We retrospectively reviewed pretreatment computed tomography/magnetic resonance imaging scans of all T4 HPV+ OPSCC patients treated with definitive (chemo)radiation therapy in 2010 to 2021. Nine T4-defining features were assessed: involvement of genioglossus, hyoglossus, palatoglossus, styloglossus, pterygoid muscles (medial and lateral), bone (mandible, hard palate, pterygoid plates, skull base), larynx, nasopharynx, and carotid artery. The prognostic validity of each T4-defining feature was evaluated by comparing the risk of disease progression with that of T3 disease using univariable analysis. Multivariable analysis, stratified by treatment and adjusted for gross tumor volume of the primary lesion (GTVp), estimated the adjusted hazard ratio (aHR) for risk of disease progression associated with each of the 9 features within T4 disease.

RESULTS

A total of 522 cases were included (T4 [239], T3 [283]). The frequencies of individual T4-defining features were as follows: hyoglossus (71%), palatoglossus (71%), styloglossus (68%), genioglossus (38%), carotid encasement (23%), pterygoid muscle (14%), larynx (12%), nasopharynx (8%), and bone (4%). All 9 T4-defining features were associated with higher risk of cancer progression versus T3 (all P < .01). Among T4 cases, invasion of nasopharynx (aHR, 2.42; 95% CI, 1.20-4.90; P = .014) and genioglossus (aHR, 1.99; 95% CI, 1.26-3.14; P = .003) conferred greater risk of disease progression versus other T4-defining features.

CONCLUSIONS

All radiologic UICC/AJCC T4-defining features have worse outcomes compared to T3 disease, supporting their retention within the T4 category. Among T4 cases, worse outcomes were observed in cases with deep tongue muscle invasion (genioglossus) and nasopharyngeal extension.